The present invention relates to a manufacturing process of a metal complex salt compound with a particular monoazo compound coordinated to a particular metal, more specifically to a manufacturing process which is industrially advantageous and which enables the reduction of the environmental load, and to a charge control agent which can be produced by said manufacturing process, and a toner for developing electrostatic latent images containing said charge control agent.
In copying machines, printers and other instruments based on electrophotography, various toners containing a coloring agent, a fixing resin and other substances are used to visualize the electrostatic latent image formed on the photoreceptor having a light-sensitive layer containing an inorganic or organic photoconductive substance.
Toner chargeability is a key factor in electrostatic latent image-developing systems. Thus, to appropriately control or stabilize the amount of charges of a toner, a charge control agent providing a positive or negative charge is often added to the toner.
Of the conventional charge control agents in actual application, those providing a negative charge for a toner include monoazo compound metal complex salt dyes, and metal complexes or metal salts of aromatic hydroxycarboxylic acids such as alkylsalicylic acids.
However, many of the metal complexes of azo dye structure which have been proposed as charge control agents are generally unstable; for example, they are likely to be decomposed or deteriorated to lose their charge control capability when exposed to mechanical friction or impact, electric impact, light irradiation, temperature or humidity changes, etc. Even with a practically applicable charge-providing property, such metal complexes are often unsatisfactory in charge stability or contain impurity chemical substances having no charge control effect depending on the method and conditions of production, thus posing various problems concerning the stability and reliability of their quality as charge control agents. In addition, there has recently been a demand for charge control agents considering environmental concern and safety to the human body.
As charge control agents capable of resolving some of such problems, metal complex salt dyes (compounds) of the following structures, for example, are available. 
[In the two formulas, A+ is a counter ion such as H (hydrogen), an alkali metal, ammonia or an amine.]
Such metal complex salt dyes are so-called 2:1 type azo metal complex dyes with two molecules of monoazo dye coordinated to one trivalent metal atom.
Traditionally, the commonly used manufacturing process for this kind of metal complex salt dyes has been based on, for example, processes 1 and 2 below.
1) A process wherein a monoazo compound (diazotizing coupling product) having a metallizable group constituting the ligand of the metal complex salt dye is prepared: An aromatic amine derivative having a group suited for the formation of a metal complex salt is first diazotized. The resulting diazonium salt is coupled to a coupling component having a group suited for the formation of a metal complex salt. The monoazo compound produced by coupling is isolated from the aqueous medium.
2) A process wherein the monoazo compound prepared is metallized: The monoazo compound is dissolved or suspended in water, a water-miscible organic solvent, or water-water-miscible organic solvent. Using a metallizing agent under the reaction conditions, the monoazo compound is metallized. The resulting metal complex salt dye is isolated.
However, manufacturing processes like that described above are faulty in that large amounts of waste liquid are produced, and that the process for isolating the coupling product by salting-out and filtration takes much time and material, and are problematic in that production cost increases as organic solvent separation and recovery and waste liquid treatment are necessary for the process for carrying out a metallizing reaction using a water-miscible organic solvent, and that organic solvent recovery is hampered as large amounts of water is necessary.
As a manufacturing process free from such drawbacks, there may be mentioned the manufacturing process disclosed in Japanese Patent Examined Publication No. 22969/1996, which corresponds to U.S. Pat. No. 5,204,453, issued Apr. 20, 1993. Using this method, a 1:2 type metal complex salt azo dye is obtained by performing diazotization, coupling and metallization in a one pot method (1-container method) without isolating the coupling product, in an aqueous system.
However, when a one-pot manufacturing process in common use or one based on a reaction in an aqueous system like that described in Japanese Patent Examined Publication No. 22969/1996, is applied to the production of the metal complex salt compound desired in the present invention, the following drawbacks are noted.
i) The solubility of the coupling component is low.
ii) The production rate of the coupling product is slow, and the purity is low.
iii) In the subsequently metallized metal complex salt compound, there observed are impurity substances such as unreacted coupling product and inorganic salts.
In addition, certain conventional metal complex azo dyes for toners, which are excellent in fine pulverizability because of generally hard crystallinity, have problems to be resolved; for example, when used in toners as charge control agents, they show insufficient compatibility (wettability) with the resins for toners, which in turn results in relatively slow charge rise speeds; and the hard crystal is likely to drop off from toner particles during frictional charging as it is partially exposed to the surface of toner particles.
The present invention was developed in view of the above problems in the prior art. Accordingly, it is an object of the present invention to provide a high-purity metal complex salt compound with a monoazo compound having a particular alkyl group (4 to 12 carbon atoms) serving as a ligand, in a high yield in a short time.
It is another object of the present invention to reduce the environmental load by recovering and reusing the solvent.
It is still another object of the present invention to provide a charge control agent which is excellent in charge-providing property and stability and good in dispersibility and wettability in resins for toners, which, when used in a toner, produces a rapid rise of charging and is unlikely to drop off from toner particles during frictional charging, and which is excellent in storage stability (temporal stability of charge control characteristic) and durability (charge control characteristic stability in the case of multiple repeated use of toner) and very safe as it contains no harmful heavy metals and yields negative results in the Ames test, and a method for its production.
It is a further object of the present invention to provide a toner for developing electrostatic images which assures fixability and offset resistance over a wide range of temperature, which is excellent in environmental resistance (charge characteristic stability to temperature and humidity changes), storage stability (temporal stability of charge characteristic) and durability (charge characteristic stability in the case of multiple repeated use of toner), which shows a rapid rise of charging, and which is capable of forming stable copied images.
(1) The process for manufacturing of the present invention for accomplishing the above objects is a process for manufacturing a metal complex salt compound of General Formula (I) below, which comprises a metallizing reaction for metallizing a monoazo compound of Formula (II) with iron, nickel, aluminum, titanium or zirconium to produce a metal complex salt compound, in which metallizing reaction a monohydric or dihydric alcohol is used as a reaction-promoting solvent: 
in Formula (I),
R is a normal or branched alkyl group having 4 to 12 carbon atoms;
Y is halogen atom or normal or branched alkyl group having 1 to 5 carbon atoms;
each of p and q shows the number of monoazo compounds coordinated to the metal M; p is 1, 2, 3 or 4; q is 0, 1, 2 or 3; p+q is an integer of 1 to 6;
each of L1 and L2 is xe2x80x94Oxe2x80x94;
one of L3 and L4 is xe2x80x94Oxe2x80x94, while the other is an xe2x80x94OH group or an xe2x80x94Oxe2x88x92 ion;
M is iron, nickel, aluminum, titanium or zirconium;
(Mx+)m represents an m number of metals of atomic valence x; m is an integer of 1 to 4; x is an integer of 2 or more;
Zxe2x88x92 is the negative charge in the parentheses; (A+)n is a hydrogen ion (H+) or an alkali metal ion (Na+, K+, etc.), n=Z; 
in Formula (II),
R is a normal or branched alkyl group having 4 to 12 carbon atoms;
Y is halogen atom or normal or branched alkyl group having 1 to 5 carbon atoms.
(1-1) The metal complex salt compound manufacturing process of Term (1) preferably comprises a step of cooling the reaction mixture and separating the metal complex salt compound precipitated, from the cooled mixture, after the aforementioned metallizing reaction is carried out using a monohydric alcohol as a reaction-promoting solvent.
(1-2) In the metal complex salt compound manufacturing process of Term (1-1), it is preferable that the metallizing reaction is followed by separating the metal complex salt compound precipitated, from the aforementioned cooled reaction mixture, recovering the monohydric alcohol in the form of an azeotrope with water, and reusing the monohydric alcohol in the azeotrope as the entire reaction-promoting solvent or a part thereof.
(1-3) The metal complex salt compound manufacturing process of Term (1) preferably comprises a step of diazotizing coupling reaction to produce a monoazo compound of Formula (II), in which diazotizing coupling reaction a monohydric or dihydric alcohol is used as a reaction-promoting solvent.
Although the reaction-promoting solvent used in the diazotizing coupling reaction is preferably the same as the reaction-promoting solvent used in the metallizing reaction, it may be different from the latter.
(1-4) The metal complex salt compound manufacturing process of Term (1-3) preferably comprises a step of cooling the reaction mixture and separating the metal complex salt compound precipitated, from the cooled mixture, after the aforementioned diazotizing coupling reaction and metallizing reaction are carried out using a monohydric alcohol as a reaction-promoting solvent.
(1-5) In the metal complex salt compound manufacturing process of Term (1-4), it is preferable that the metallizing reaction is followed by separating the metal complex salt compound precipitated, from the aforementioned cooled reaction mixture, recovering the monohydric alcohol in the form of an azeotrope with water, and reusing the monohydric alcohol in the azeotrope as the entire reaction-promoting solvent or a part thereof.
(1-6) In the metal complex salt compound manufacturing process of Term (1-4) or (1-5), it is preferable that the aforementioned diazotizing coupling reaction is followed by separating the monoazo compound precipitated, from the reaction mixture, recovering the monohydric alcohol in the form of an azeotrope with water, and reusing the monohydric alcohol in the azeotrope as the entire reaction-promoting solvent or a part thereof.
(1-7) In the metal complex salt compound manufacturing process of Term (1-2), (1-5) or (1-6), it is preferable that the water content in the aforementioned azeotrope is not more than 20% by weight.
(1-8) R in Terms (1) to (1-7) above is preferably a tert-octyl group.
(1-9) In the metal complex salt compound manufacturing process of Term (1) to (1-8) above, it is preferable that Y is chlorine atom.
(1-10) In the metal complex salt compound manufacturing process of Term (1) to (1-9) above, it is preferable that the reaction-promoting solvent is one or more monohydric alcohols selected from the group consisting of ethanol, propanol, 2-propanol, butanol, isobutanol, sec-butanol, tert-butanol, amyl alcohol and isoamyl alcohol.
(1-11) The alcohol serving as a reaction-promoting solvent in Term (1-10) above is preferably 2-propanol.
(1-12) The metal complex salt compound manufacturing process of Terms (1-3), (1-4), (1-5) or (1-6) preferably comprises a step of obtaining a monoazo compound using 4-chloro-2-aminophenol as a diazo component, 6-tertiary octyl-2-naphthol as a coupling component, and 2-propanol as a reaction-promoting solvent; and a step of metallizing the monoazo compound obtained, in an aqueous solvent and 2-propanol as a reaction-promoting solvent.
(1-13) In the metal complex salt compound manufacturing process of Term (1) to (1-12) above, it is preferable that iron chloride is used as a metallizing agent in the metallizing reaction.
(2) The charge control agent of the present invention comprises a metal complex salt compound of General Formula (I) below as an active ingredient, and containing substantially no monoazo compound constituting the ligand thereof: 
in Formula (I),
R is a normal or branched alkyl group having 4 to 12 carbon atoms;
Y is halogen atom or normal or branched alkyl group having 1 to 5 carbon atoms;
each of p and q shows the number of monoazo compounds coordinated to the metal M; p is 1, 2, 3 or 4; q is 0, 1, 2 or 3; p+q is an integer of 1 to 6;
each of L1 and L2 is xe2x80x94Oxe2x80x94;
one of L3 and L4 is xe2x80x94Oxe2x80x94, while the other is an xe2x80x94OH group or an xe2x80x94Oxe2x88x92 ion;
M is iron, nickel, aluminum, titanium or zirconium;
(Mx+)m represents an m number of metals of atomic valence x; m is an integer of 1 to 4; x is an integer of 2 or more;
Zxe2x88x92 is the negative charge in the parentheses; (A+)n is a hydrogen ion (H+) or an alkali metal ion (Na+, K+, etc.), n=Z.
This charge control agent contains the aforementioned metal complex salt compound at a high purity (not less than about 90% by weight, preferably not less than about 95% by weight, more preferably not less than about 99% by weight), and can be produced by the metal complex salt compound manufacturing process described in Term (1) to (1-13) above.
(2-1) M in Term (2) above is desirably trivalent or divalent iron.
(2-2) The pH of the charge control agent of Term (2) or (2-1) above is preferably 7 to 12.
(2-3) The charge control agent of Term (2) to (2-2) above yields negative results in the Ames test.
(3) The toner of the present invention for developing electrostatic images contains the charge control agent of Term (2) to (2-3) above, a resin for toners, and a coloring agent.
According to the process for manufacturing of the present invention, a metal complex salt compound whose content of unreacted monoazo compound is much smaller than that with conventional compounds, or a metal complex salt compound containing substantially no unreacted monoazo compound, can be produced in a high yield in a short time, and the products obtained by this manufacturing process is excellent in charge control stability, charge rise speed, storage stability, durability, etc., as charge control agents.
According to the invention of Term (1-1) or (1-4) above, a metal complex salt compound of better purity can be produced in a high yield in a short time, and the products obtained by these manufacturing processes are more excellent in charge control stability, charge rise speed, storage stability, durability, etc., as charge control agents.
In addition, according to the invention of Term (1-2), (1-5) or (1-6), significant production cost reduction and environmental load mitigation can both be realized by reusing the monohydric alcohol in the azeotrope recovered.
The charge control agent of the present invention is excellent in negative charge-providing property and stability and good in dispersibility and wettability in resins for toners. When used in a toner, it produces a rapid rise of charging and is unlikely to drop off from toner particles during frictional charging. It is also excellent in storage stability and durability and very safe as it contains no harmful heavy metals and yields negative results in the Ames test.
Containing the charge control agent of the present invention, the toner of the present invention for developing electrostatic images assures fixability and offset resistance over a wide range of temperature, is excellent in environmental resistance, storage stability and durability, shows a rapid rise of charging, and is capable of constantly forming copied images.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.